JP4635210B2 - Radiation or neutron detector using optical fiber - Google Patents

Description

  The present invention detects a two-dimensional image of radiation or neutrons by detecting fluorescence emitted from a phosphor or scintillator using a wavelength shift fiber in a radiation or neutron detector using an optical fiber. About.

Conventionally, as a radiation and neutron detector using an optical fiber, a radiation image detector and a neutron image detector using a phosphor or scintillator and a wavelength shift fiber have been used [Nucl. Instr. And Meth., A430 (1999) 311-320, Japanese Patent Application No. 10-366679, Japanese Patent Application 2000-259443]. These detectors are characterized in that position information is obtained by a cross fiber reading method, and as shown in FIG. 17, wavelength shift fiber bundles are arranged in a plane at right angles on the upper and lower surfaces of a phosphor sheet or scintillator plate, The radiation incident position is determined by the coincidence method and the radiation image is detected. Alternatively, as shown in FIG. 18, two types of wavelength shift fiber bundles, a short wavelength side fluorescence detection wavelength shift fiber and a long wavelength side fluorescence wavelength shift fiber, are arranged in a plane at right angles, and a phosphor sheet thereon Alternatively, a scintillator plate is arranged, the radiation incident position is determined by the coincidence method, and the radiation image is detected.

  However, the wavelength shift fiber used in these detectors absorbs the fluorescence emitted from the phosphor or scintillator once, converts it to a wavelength longer than the absorbed wavelength, and detects the fluorescence. As the wavelength of the photomultiplier tube is increased, the photomultiplier tube normally used as a photodetector has been used outside the detection sensitivity region. In particular, when a wavelength shift fiber is used for a neutron detector, the wavelength shift fiber is sensitive to gamma rays, which causes a gamma ray background.

  Further, in order to increase the detection sensitivity by the above method, a sensor composed of a phosphor or scintillator and a wavelength shift fiber is used in a stacked manner, so that the number of wavelength shift fibers is increased and the detection structure is complicated.

  On the other hand, in the case of a detector using a wavelength shift fiber or an optical fiber, when the optical fiber is bent at a right angle or an angle close to a right angle, it is bent at a bending radius of several centimeters or more due to the limitation of the bending angle of the optical fiber. For this reason, there was a problem in making the detector compact.

  Furthermore, in the case of a radiation image detector or neutron image detector using a phosphor or scintillator and a wavelength shift fiber, the fluorescence that is absorbed in the process of transmitting the wavelength shifted fluorescence that lengthens the wavelength shift fiber and reaches the detector. Because it decreases, it could not be used for too long. In addition, as described above, since the wavelength shift fiber itself has gamma ray sensitivity, when used in a neutron detector, the gamma ray background becomes a problem, and when used in a gamma ray detector, gamma ray is a problem. It was a background to the image. Because of these problems, the wavelength shift fiber has to be used as short as possible.

Instead of the wavelength-shifted fiber, the fluorescence emitted from the phosphor or scintillator
Radiation or neutrons are detected by scraping the side of a transparent optical fiber and using an optical fiber that allows fluorescence to enter from the side and guide the fluorescence to both ends of the wavelength shift fiber. When detecting a radiation image or a neutron image, a gamma ray background is obtained by using at least one of the two wavelength-shifted fiber bundles arranged at right angles, and using an optical fiber obtained by scraping the side surface of the transparent optical fiber. Reduce.

  In order to increase the detection sensitivity of a radiation image detector or neutron image detector, instead of simply stacking sensors, the sensitivity of two wavelength-shifted fiber bundles arranged at right angles is aligned and fluorescence is emitted from the top and bottom surfaces. It can be detected and realized by arranging phosphors or scintillators on both sides.

  When bending an optical fiber, which is indispensable for downsizing the detector, when the diameter of a circular fiber is 1 mm or less, or when the length of a side is 1 mm or less for a square fiber, select the optical fiber material. Even when bent to a right angle or an angle close to a right angle, it was found that about 20 to 50% of the fluorescence is transmitted. Therefore, the optical fiber is bent and used.

  When the wavelength shift fiber is lengthened, the gamma ray background increases. In this case, the diameter of the transparent optical fiber is larger than the wavelength shift fiber to be connected, and grease is used for the connection.

Example 1
As Example 1, a square transparent optical fiber having a side length of 0.5 mm was used, and one side of the four side surfaces of the transparent optical fiber had a length in the range of 5 cm, and a thickness of 20 μm. FIG. 1 is a structural diagram of a side-surface detection optical fiber having a structure in which white paper is used as a light reflecting material on the side surface opposite to the side surface that has been scraped off. As the optical fiber, a square transparent optical fiber BCF-98 having a side of 0.5 mm manufactured by Bicron, USA is used. The position distribution characteristics with respect to fluorescence of this side-surface light detection type optical fiber were measured by improving the fluorometer. As a result of the measurement, as shown in FIG. 2, a substantially uniform distribution was obtained in the range of 5 cm. The detection efficiency was about 0.5% as a result of calibration using a 678 nm laser light source.

In this embodiment, a neutron detector that detects neutrons, detects eight neutrons by detecting fluorescence emitted from a neutron detection sheet in which phosphors and neutron converters are mixed, using eight side-surface detection type optical fibers. The embodiment is shown in FIG. As the detection sheet, ZnS: Ag is used as a phosphor, and ⁶ LiF is used as a neutron converter, and mixed and applied to a 1 mm-thick aluminum plate, BC-702 manufactured by Bikinron, USA. As a result, a neutron detector having a detection portion having a width of 4 mm and a length of 4 cm could be constructed. The optical fiber has a length of 1 mm, and a photomultiplier tube is connected to the other end. R647P manufactured by Hamamatsu Photonics is used as the photomultiplier tube. The output signal from the photomultiplier tube has a fluorescence lifetime of ZnS: Ag of 200 ns, so it is amplified by a spectroscopic amplifier set to a waveform shaping time constant of 0.5 μs and shaped in waveform. Thereafter, a neutron signal can be obtained by using a waveform discriminator that extracts a pulse signal of a certain signal level or higher.

(Example 2)
As Example 2, white paper, a Teflon (registered trademark) plate, a white paint, an aluminum foil, or a polystyrene plate is used as the reflective material provided on the side opposite to the side of the transparent optical fiber that has been cut off. Table 1 shows the results of comparative measurements at the location of the 2 cm portion of the fiber. In addition, the results of the black plate and the aluminum plate are also shown for comparison. While light detection efficiency of 0.4% to 0.5% can be obtained by incidence from the scraped surface, 0.04% is obtained when a material that does not reflect irregularly such as a black plate and an aluminum plate is used.
Thus, the detection efficiency is almost half or 0.2%, which shows that the present example is effective.

(Example 3)
As Example 3, in the case of using phosphor powder instead of white paper or the like as the material for irregularly reflecting the light provided on the surface opposite to the scraped side surface in Example 1 above, based on FIG. explain. As can be seen from FIG. 4, phosphors are arranged on both the side surface and the back surface thereof. As shown in Table 1, the light detection efficiencies of the phosphors incident from the scraped surface and incident from the back surface thereof are 0.55% and 0.33%, respectively. As a phosphor, a neutron detection medium (thickness: 0) in which ZnS: Ag and ⁶ LiF which is a neutron converter are mixed.
. 4mm), when neutrons are incident, 1500 or more lights are emitted. Even with a detection efficiency of 0.33%, five photons are transmitted to the photodetector. When a photomultiplier tube is used as the photodetector, the quantum efficiency is about 20%. Therefore, one photon electric signal is obtained, and neutrons can be sufficiently detected by using the photon counting method. Since this detection medium is opaque, the thickness cannot be increased to 0.5 mm or more. Therefore, by adopting this embodiment, the thickness is doubled and a neutron detector having a thickness of substantially 0.8 mm is obtained. Thus, a neutron detector having a detection efficiency almost doubled can be configured.
Example 4
As Example 4, a square transparent optical fiber having a side length of 0.5 mm was used, and one of the four side surfaces of the transparent optical fiber had a length in the range of 12 cm, and a thickness of 30 μm. A side light detection type having a structure in which a white paint is applied as a light reflecting material to the side surface opposite to the side surface that has been scraped off is used. As the optical fiber, a square transparent optical fiber BCF-98 having a side of 0.5 mm manufactured by Bicron, USA is used. The position distribution characteristics of the side-incident optical fiber with respect to fluorescence were measured by improving the fluorometer. As a result of the measurement, as shown in FIG. 5, a distribution almost in an exponential function was obtained. This is because when the optical fiber is scraped about 15 cm long compared to the first embodiment, the detection efficiency at the beginning of cutting is high, and the detection efficiency decreases as it goes further. For this reason, light detection is performed from both ends of the optical fiber. When light is detected from both ends of the optical fiber using the distribution of FIG. 5, the incident position distribution characteristic as shown in FIG. 5 is obtained. As a result, it was confirmed that the detection efficiency for light can be used as a side detection type optical fiber that hardly depends on the incident position over a wide area.
(Example 5)
As Example 5, the structure of a two-dimensional radiation image detector according to the present invention is shown in FIG. In this embodiment, alpha rays are detected as radiation, and ZnS: Ag which is commonly used as a phosphor for an alpha ray detection medium is used. A portion obtained by scraping one side surface of four side surfaces of two transparent optical fibers as shown in FIG. 6 on the lower surface of a phosphor sheet made of ZnS: Ag having a thickness of 0.2 mm is used as a detection portion. The side surface detection type optical fiber bundles are arranged in parallel and arranged at right angles.

The center of the fluorescence wavelength of ZnS: Ag is 450 nm, and fluorescence having a wide wavelength from 360 nm to 540 nm is generated, and the fluorescence lifetime is 200 ns.
A clear fiber of BCF-98 manufactured by US Micron Corporation is used as a material of the side surface detection type optical fiber in which a portion of one of the four side surfaces of the transparent optical fiber is cut off. Regarding the thickness of the clear fiber, since the thickness of the phosphor sheet is 0.2 mm, a square fiber having a piece length of 0.5 mm is used. The clear fibers of the two optical fiber bundles arranged are connected to the photodetector one by one.

As a photodetector for detecting the fluorescence emitted from the side surface detection type optical fiber made of BCF · 98, H6568 manufactured by Hamamatsu Photonics, which is a 16-channel photomultiplier tube, can be used. Each photoelectric signal output from the photomultiplier tube is amplified by an amplifier, and then converted into a digital pulse signal by a wave height discriminator, to become an X-axis pulse signal and a Y-axis pulse signal. The two-dimensional incident position of the radiation is determined by measuring the X-axis pulse signal and the Y-axis pulse signal simultaneously. If the coincidence time (coincidence time) is 600 ns, which is three times the fluorescence lifetime of ZnS: Ag, sufficient coincidence can be performed, and a radiation image can be detected.
(Example 6)
As Example 6, the structure of a two-dimensional radiation image detector according to the present invention is shown in FIG. In this embodiment, alpha rays are detected as radiation, and ZnS: Ag which is commonly used as a phosphor for an alpha ray detection medium is used. A wavelength shift fiber for short wavelengths having sensitivity on the short wavelength side of fluorescence emitted from these detection media as shown in FIG. 7 on the lower surface of a phosphor sheet made of ZnS: Ag having a thickness of 0.2 mm; Side surface detection type optical fibers having a detection part as one of four side surfaces of a transparent optical fiber are arranged in parallel and arranged at right angles.

The center of the fluorescence wavelength of ZnS: Ag is 450 nm, and fluorescence having a wide wavelength from 360 nm to 540 nm is generated, and the fluorescence lifetime is 200 ns.
As the wavelength shift fiber for a short wavelength, BCF-92 manufactured by US Bron Inc. which is sensitive to fluorescence from 350 nm to 440 nm and converts the wavelength to fluorescence of 490 nm is used. In addition, as a material of the side surface detection type optical fiber in which a portion of one of the four side surfaces of the transparent optical fiber is cut off is used as a detection portion, a clear fiber of BCF-98 manufactured by US Micron Corporation is used. About the thickness of a wavelength shift fiber and a clear fiber, since the thickness of a fluorescent substance sheet is 0.2 mm, the length of one piece is 0.5 mm square fiber. The arranged wavelength shift fiber and clear fiber are connected to the photodetector one by one.

The subsequent configuration and operation from the photodetector are the same as those in the fifth embodiment.
(Example 7)
As Example 7, the structure of a two-dimensional radiation image detector according to the present invention is shown in FIG. In this embodiment, alpha rays are detected as radiation, and ZnS: Ag which is commonly used as a phosphor for an alpha ray detection medium is used. On the lower surface of a phosphor sheet made of ZnS: Ag having a thickness of 0.2 mm, a wavelength having sensitivity to fluorescence emitted from these detection media as shown in FIG. 8 and absorption efficiency of 50% or less of fluorescence. Side surface detection type optical fibers having a detection part as a part of one of the four side surfaces of the shift fiber and the transparent optical fiber are arranged in parallel and arranged at right angles.

The center of the fluorescence wavelength of ZnS: Ag is 450 nm, and fluorescence having a wide wavelength from 360 nm to 540 nm is generated, and the fluorescence lifetime is 200 ns.
As a wavelength shift fiber that is sensitive to fluorescence emitted from the detection medium and has an absorption efficiency of 50% or less of fluorescence, Y-made by Kuraray Co., Ltd., which is sensitive to fluorescence from 390 nm to 500 nm and converts the wavelength to fluorescence of 520 nm. 8 (organic phosphor concentration 100 ppm) is used. In addition, as a material of the side surface detection type optical fiber in which a portion of one of the four side surfaces of the transparent optical fiber is cut off is used as a detection portion, a clear fiber of BCF-98 manufactured by US Micron Corporation is used. About the thickness of a wavelength shift fiber and a clear fiber, since the thickness of a fluorescent substance sheet is 0.2 mm, the length of one piece is 0.5 mm square fiber. The arranged wavelength shift fiber and clear fiber are connected to the photodetector one by one.

The subsequent configuration and operation from the photodetector are the same as those in the fifth embodiment.
(Example 8)
As an eighth embodiment, an example configured based on the fifth embodiment will be described with reference to FIG.

In this embodiment, neutrons are detected. As the phosphor for the neutron detection medium, ZnS: Ag is used as the phosphor and the thickness of 0.4 mm using ⁶ LiF as the neutron converter.
BC-702 manufactured by US Bicycleron Co., Ltd. is used. On the lower surface of this neutron detection medium, as shown in the figure, side-surface detection type optical fiber bundles each having a detection portion that is a portion of one of the four side surfaces of two transparent optical fibers arranged in parallel and perpendicular to each other are shown. To place. The structure is such that BC-702 manufactured by Bicron, USA is disposed as the phosphor for the neutron detection medium behind the two optical fibers for light detection. By adopting the present embodiment, the thickness of the neutron detection medium is doubled, and a neutron image detector having a thickness of substantially 0.8 mm can be obtained, and the neutron image detector in which the detection efficiency is almost doubled. Can be configured.

  On the other hand, in order to realize the present embodiment, sufficient light can be obtained when the back side of the side light-detecting optical fiber cut off by the side-light-detecting optical fiber is used as the detection part. Although it is indispensable to obtain detection efficiency, as described in Example 3, it was taken at a portion at a position of 2 cm of the side surface detection type optical fiber in which a portion obtained by scraping one side surface of the four side surfaces is a detection portion. The light detection efficiency in the case of incidence from the back surface is sufficient at 0.3%. In addition, the light detection efficiency of the side light detection type optical fiber placed on the lower side when the two side light detection type optical fibers are overlapped is shown in Table 2. It has been found that the direct-incidence or slightly increased characteristics are exhibited. The reason for the slight increase is considered to be scattering by the side-surface detection type optical fiber placed on top. From the above, it has been found that light detection on both sides using an optical fiber in which two side surface light detection type optical fibers are overlapped is possible.

Example 9
As Example 9, the structure of a neutron image detector according to the present invention is shown in FIG.
In this example, neutrons are detected, and as the phosphor for the neutron detection medium, ZnS: Ag is used as the phosphor and the thickness of 0.4 mm using ⁶ LiF as the neutron converter.
BC-702 manufactured by US Bicycleron Co., Ltd. is used. On the lower surface of this neutron detection medium, as shown in the figure, wavelength shift fibers having sensitivity to fluorescence emitted from these two detection media and having an absorption efficiency of 50% or less of fluorescence are arranged in parallel and arranged at right angles. . A wavelength-shifted fiber that is sensitive to fluorescence emitted from the detection medium and has an absorption efficiency of 50% or less of fluorescence, is sensitive to fluorescence from 390 nm to 500 nm, and converts the wavelength to 520 nm fluorescence. 8 (organic phosphor concentration 100 ppm) is used. The absorption characteristics of this wavelength shift fiber are shown in FIG. It can be seen that the absorption characteristic is 50% or less. It is set as the structure which arrange | positioned BC-702 by USA bicron company as a fluorescent substance for neutron detection media behind the two wavelength shift fiber bundles arrange | positioned at right angle. In this configuration, since light reading using two wavelength shift fiber bundles is possible from both sides, the thickness of the neutron detection medium is doubled, and a neutron image detector having a thickness of substantially 0.8 mm Thus, a neutron image detector having a detection efficiency almost doubled can be configured.
(Example 10)
Usually, the minimum bending radius of an optical fiber including a wavelength shift fiber requires 10 mm even for an optical fiber having a diameter of 0.5 mm. However, when an optical fiber is used in combination with a phosphor or a scintillator, this bending diameter becomes a dead space, so it is necessary to reduce the bending diameter. The core material of the optical fiber is polystyrene or polymethylmethacrylate resin. In the case of a circular optical fiber, the diameter is 0.25 mm to 1 mm. In the case of a square optical fiber, the length of one side is 0.25 mm. The optical transmission characteristics were measured when the optical fiber was bent to an angle of 45 to 105 degrees with an optical fiber of 1 mm and a bending diameter in the range of 1 to 1.5 times the diameter or length of one side. As an optical fiber, a clear fiber of BCF-98 manufactured by US Micron, which is a square optical fiber having a side of 0.5 mm, was used. As a result, it was found that by selecting the material of the optical fiber as shown in FIG. 12, a transmittance of nearly 50% can be obtained even when bent to 90 degrees.

Based on these results, the neutron detector shown in FIG. In this embodiment, neutrons are detected. As the phosphor for the neutron detection medium, Zn-S: Ag is used as the phosphor, and BC-702 having a thickness of 0.4 mm using ⁶ LiF as the neutron converter is used. The area is 1 cm ² . A wavelength shift fiber bent at 90 degrees as shown in the figure is used on the lower surface of the neutron detection medium. As the wavelength shift fiber, BCF-92 manufactured by US-based Bron Inc. which is sensitive to fluorescence from 350 nm to 440 nm and converts the wavelength to fluorescence of 490 nm is used. A square wavelength shift fiber having a side of 0.5 mm is used, and the other end of the bent wavelength shift fiber is connected to a photomultiplier tube as shown in the figure. Twenty wavelength shift fibers are used to make the detection part 10 mm square. As the photomultiplier tube, R647P manufactured by Hamamatsu Photonics having a diameter of 1.3 cm can be used. With this configuration, a small neutron detector with no dead space can be manufactured.

  In addition, when the core material of the optical fiber of the example is polystyrene, it is indispensable to use a material in which polystyrene molecules are continuously bonded because the bending strength is strong. This material is used for clear fiber. In the case of Kuraray Co., Ltd., the S type is a material in which polystyrene molecules are continuously bonded.

In the case of this embodiment, instead of the wavelength shift fiber, one of the four side surfaces of the transparent optical fiber described in the first embodiment is scraped off to a thickness of 20 μm and a portion having a length in the range of 1 cm. A side incident optical fiber having a structure in which white paper is used as a light reflecting material on the opposite side surface can be used.
(Example 11)
As Example 11, the structure of a neutron image detector according to the present invention is shown in FIG. As shown in Example 10, it is possible to arrange two types of optical fiber bundles by arranging two or more optical fibers having a bent portion in an angle range of 45 ° to 105 ° without any gaps and three-dimensionally intersecting. This is an embodiment that enables detection of a neutron image.

As the neutron detection medium, ZnS: Ag is used as the phosphor, ⁶ LiF is used as the neutron converter, and the detector is applied to Pyrex (registered trademark) glass to a thickness of 0.2 mm. The detection area is 8 mm × 8 mm. As the wavelength shift fiber, 16 square wavelength shift fibers each having a side of 0.5 mm are used for the X axis and the Y axis, respectively. In this embodiment, a crossed fiber method is used in which imaging is performed with a neutron detection medium sandwiched between a Y-axis wavelength shift fiber and an X-axis wavelength shift fiber. As the Y-axis wavelength shift fiber and the X-axis wavelength shift fiber, BCF-92 manufactured by US Micron Corporation that is sensitive to fluorescence from 350 nm to 440 nm and converts the wavelength to 490 nm fluorescence is used. Regarding the thickness of the wavelength shift fiber, since the thickness of the phosphor sheet is 0.2 mm, a square fiber having a piece length of 0.5 mm is used. The bending angle is 90 degrees.

  Aluminum is used as the mount to be fixed. Since the length of one side is 0.5 mm, it is multiplied by 1.42 and considering the drilling accuracy, holes with a diameter of 0.8 mm are alternately formed in 4 rows at intervals of 1 mm as shown in the figure. In this way, square wavelength shift fibers with a side of 0.5 mm can be arranged in parallel without gaps, and the detector can be made very compact by using the wavelength shift fibers bent at 90 degrees. Can do. This is particularly effective when the number of fibers is 100 or more.

About this neutron image detector, 1.5 mmφ cold neutron beam was measured in the cold neutron radiography facility (CNRF) of JAERI's nuclear reactor JRR-3M. The measurement results are shown in FIG. It was found that 0.6 mm was obtained as the position resolution, and the effectiveness of this example was confirmed.
(Example 12)
In this embodiment, when detecting fluorescence from a scintillator or phosphor as a detection medium of radiation or neutron using a wavelength shift fiber, the wavelength shift fiber itself becomes a gamma ray detector. It is used to improve that the background of gamma rays is received and that the transmittance of the wavelength-shifted fluorescence of the wavelength-shifted fiber is deteriorated if it is too long at the same time. In addition, a part that detects fluorescence using a wavelength shift fiber or a side-light-detecting type optical fiber and a part that guides the detected fluorescence to the photodetector are manufactured separately, thereby facilitating maintenance. Can do.

A configuration of the twelfth embodiment will be described with reference to FIG. In this embodiment, a neutron image detector for detecting neutrons will be described.
As the phosphor for the neutron detection medium, Zn-S: Ag is used as the phosphor, and BC-702 having a thickness of 0.4 mm using ⁶ LiF as the neutron converter is used. On the lower surface of this neutron detection medium, as shown in the figure, side-surface detection type optical fiber bundles each having a detection portion that is a portion of one of the four side surfaces of two transparent optical fibers arranged in parallel and perpendicular to each other are shown. To place.

  A clear fiber of BCF-98 manufactured by US Micron Corporation is used as a material of the side surface detection type optical fiber in which a portion of one of the four side surfaces of the transparent optical fiber is cut off. Regarding the thickness of the clear fiber, since the thickness of the phosphor sheet is 0.2 mm, a square fiber having a piece length of 0.5 mm is used. The clear fibers of the two optical fiber bundles arranged have a fixed length as shown in the figure, and the end faces are polished. This block is a detection unit block.

  On the other hand, a side light detection type optical fiber is connected to a transparent circular optical fiber, and a block in which the other end of the transparent circular optical fiber is guided to a photodetector is defined as a reading block. As shown in the figure, the readout block has a configuration in which an X-axis connection hole and a Y-axis connection hole are formed in the readout fiber fixing block. The position of the hole is set to a diameter slightly larger than the size of the optical fiber in accordance with the positions of the x-axis side-surface light detecting optical fiber and the Y-axis side-surface light detecting optical fiber of the detection unit block. Below that, a hole in the readout optical fiber, a transparent optical fiber having a diameter of 1 to 1.5 times its diameter in the case of a circular optical fiber, or a square wavelength are used. In the case of a shift fiber, a square wavelength shift fiber is used in a detector that detects radiation or neutrons by using a transparent circular optical fiber whose diameter is 1.42 to 2 times the length of one side. In the case of (1), a hole is made in such a size that a transparent circular optical fiber having a diameter of 1.42 to 2 times the length of one side can be fixed. The X-axis readout optical fiber and the Y-axis readout optical fiber are fixed in this hole. In the case of the present embodiment, a square fiber having a length of 0.5 mm is used for detection, so that an optical fiber esca made by Mitsubishi Rayon having a diameter of 1 mmφ can be used.

In this way, by making it possible to separate the detection block and the readout block, it is possible to easily manufacture an image detector using a large number of optical fibers. In addition, maintenance becomes easy.
(Example 13)
An embodiment in which grease is used for the connection surface between the wavelength shift fiber or the side-surface light detection type optical fiber described in the twelfth embodiment and the transparent circular optical fiber will be described.

The transmittance was measured for the case where the connection surface of the wavelength shift fiber or the side surface light detection type optical fiber and the transparent circular optical fiber was directly connected and the case where grease was used. The wavelength shift fiber used was a square fiber having a side of 0.5 mm BCF-99 manufactured by Bikeron Co., Ltd., and a 1 mmφ plastic fiber ESCA made by Mitsubishi Rayon was used as the circular clear fiber. As a result of the measurement, the transmittance when directly connected was 35%, but when the OKEN 6262A optical grease manufactured by Applied Koken was used as the grease, the transmittance was improved to 85% and almost no loss was observed. confirmed.

It is a figure which shows the structural drawing of the side incidence optical fiber of the structure which used the white paper as a light reflection material on the side surface on the opposite side to the side surface which the optical fiber was shaved off. It is a figure which shows the position distribution characteristic with respect to the light detection efficiency of a side detection optical fiber with a detection part of 5 cm. It is a figure which shows the structure of the neutron detector which detects the fluorescence discharge | released from a neutron detection sheet using a side surface detection type optical fiber, and detects a neutron. It is a figure which shows the structure of the neutron detector which has arrange | positioned fluorescent substance to both the side surface and the back noodles which shaved the optical fiber. It is a figure which shows the position distribution characteristic with respect to the light detection efficiency of the side surface detection type optical fiber whose detector part is 12 cm. It is a figure which shows the structure of the two-dimensional radiation image detector which arranged the side surface optical detection type | mold optical fiber bundle in parallel, respectively, and has arrange | positioned at right angle. It is a figure which shows the structure of the two-dimensional radiation image detector using the wavelength shift fiber for short wavelengths, and a side surface detection optical fiber. It is a figure which shows the structure of the two-dimensional radiation image detector using the wavelength shift fiber with a 50% or less absorption efficiency, and a side surface detection type | mold optical fiber. It is a figure which shows the structure of the two-dimensional neutron image detector which arrange | positioned the side surface detection type | formula optical fiber bundle in parallel, and arrange | positioned at right angles, and has arrange | positioned the neutron detection medium on the both surfaces. It is a figure which shows the structure of the two-dimensional neutron image detector which arrange | positioned the wavelength shift fiber which has the absorption efficiency of 50% or less of fluorescence in parallel, and arrange | positioned at right angles, and has arrange | positioned the neutron detection medium on the both surfaces. It is a figure which shows the absorption characteristic of Kuraray Y-8 (organic phosphor density | concentration of 100ppm). It is a figure which shows the transmission characteristic of the light at the time of bending an optical fiber at an angle of 0 degree to 110 degree | times. It is a figure which shows the structure of the neutron detector using the wavelength shift fiber bent to 90 degree | times. It is a figure which shows the structure of the neutron image detector which arranged the optical fiber with the part bent at 90 degree | times, and made the three-dimensional crossing without gap. This is an example of measurement of a 1.5 mmφ cold neutron beam using a neutron image detector in which optical fibers having portions bent at 90 degrees are arranged without gaps and three-dimensionally crossed. It is a figure which shows the structure of the neutron image detector isolate | separated into the detection part block and the read-out block. The principle of the crossed fiber method, in which wavelength-shifted fiber bundles are arranged in a plane perpendicular to the upper and temporary surfaces of the phosphor sheet or scintillator plate of the conventional method, and at the same time the radiation incident position is determined by the counting method and the radiation image is detected. FIG. Two types of wavelength shift fiber bundles, a conventional wavelength shift fiber for detecting short wavelength fluorescence and a long wavelength wavelength shift fiber, are arranged in a plane at right angles, and a phosphor sheet or a scintillator plate is arranged thereon. It is a figure which shows the principle of a back surface reading method.

Claims (1)

  In a detector that detects radiation or neutrons using a scintillator or a phosphor as a detection medium and a wavelength shift fiber as one of the constituent materials, the detection medium emits the scintillator or phosphor to the lower surface of the scintillator A wavelength-shifted fiber that is sensitive to fluorescence and has an absorption efficiency of 50% or less of fluorescence is arranged in parallel, a wavelength-shifted fiber having the same characteristics is arranged in parallel at a right angle to the back surface, and behind that, A structure in which scintillators or phosphors as detection media are arranged, and by performing simultaneous counting measurement of position pulse signals on the horizontal axis and the vertical axis obtained from these wavelength-shifted optical fibers arranged at right angles to each other, radiation or neutrons Detector characterized by being configured as a two-dimensional image detector that determines the two-dimensional incident position of

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